Shell and tube heat exchangers and similar items of fluid handling devices utilize tubes organized in bundles to conduct the fluids through the equipment. In such tube bundles, there is typically fluid flow both through the insides of the tubes and across the outsides of the tubes. The configuration of the tubes in the bundle is set by the tubesheets into which the tubes are set. One common configuration for the tubes is a square formation with the tubes set in aligned rows with tube lanes (the straight paths between the tubes) between each pair or rows, aligned orthogonally to one another. This configuration is illustrated in FIG. 1 in connection with the tube support device and locking assembly in accordance with the present invention. In this formation, each tube is adjacent to eight other tubes except at the periphery of the tube bundle and is directly opposite a corresponding tube across the tube lane separating its row from the two adjacent rows. In the triangular tube formation, the tubes in alternate rows are aligned with one another so that each tube is adjacent six other tubes (the two adjacent tubes in the same row and four tubes in the two adjacent rows).
Fluid flow patterns around the tubes as well as the changes in the temperature and density of the fluids which arise as a result of the heat exchange between the two fluids flowing in and around the tubes may give rise to flow-induced vibrations of an oscillatory nature in the tube bundle. If these vibrations reach certain critical amplitudes, damage to the bundle may result. Tube vibration problems may be exacerbated if heat exchange equipment is retubed with tubes of a different material to the original tubes, for example, if relatively stiff materials are replaced with lighter weight tubes. Flow-induced vibration may also occur when equipment is put to more severe operating demands, for example, when other existing equipment is upgraded and a previously satisfactory heat exchanger, under new conditions, becomes subject to flow-induced vibrations. Vibration may even be encountered under certain conditions when an exchanger is still in the flow stream but without heat transfer taking place.
Besides good equipment design, other measures may be taken to reduce tube vibration. U.S. Pat. No. 7,032,655 to Wanni et al., U.S. Pat. No. 7,117,935 to Wanni et al., and U.S. Pat. No. 7,128,130 to Wanni et al. disclose various tube support devices that effectively mitigate flow-induced vibration in tube bundles. These tube support devices utilize elongated members that are adapted to be received within tube lanes to engage adjacent tubes and effectively reduce vibration to improve operation.
Co-pending U.S. patent application Ser. No. 11/128,884 to Wanni et al., also discloses another tube support device, the disclosure of which is hereby incorporated in its entirety specifically by reference. This tube support device is also effective in mitigating vibration within the tube bundle to improve operation. With reference to FIG. 1, the tube support device 10 comprises an elongated flat member made up of two strips 11, 12 that are connected together back-to-back by welds or other suitable connection means. The tube support devices 10 are configured to be inserted in the tube lanes. The support devices may be inserted within each tube lane, alternating tube lanes or at locations sufficient to mitigate vibration. The tube support device 10 includes a plurality of support members 13, 14 that engage adjacent tubes 1. The support members 13, 14 are created on the face of the two strips 11, 12. Each support member has a plurality of arcuate tube-receiving saddles 15, which are sized to receive a portion of the tubes therein. The tube support devices may be secured in place by passing a cable through the ends of the support devices 10 and around the bundle.
While the cables are effective in securing the support devices within the bundle, the use of such cables has potential drawbacks. There may be difficulties associated with installing the cable around the tube bundle. The cable may fret at the point where the cable passes through an associated aperture in the support device, which could lead to the potential failure of the cable. Additionally, the flow of fluid around the tubes of the tube bundle may cause the cable to rub on the outer surface of the outermost tubes in the tube bundle, which may cause wear.
There is a need for a locking assembly for securing a tube support device in a desired location within the tube bundle that does not cause wear to the locking assembly, the tube support device and/or the tube bundle.